OSTEOLOGY. 37 
At the sixth caudal the broad diapophysis is divided into an anterior and a 
posterior portion, the latter of which becomes obsolete at the 15th, and the 
former at about the 18th vertebra. In Gymnura the diapophyses are much less 
developed, having an anterior but not a posterior origin on each vertebra, while 
the prezygapophyses, in the specimen examined, end with the third caudal. 
The chevron bones are largely developed, and as in Gymnura occur in con- 
nection with all but the few terminal vertebrae. In Gymnura, however, the 
two lateral elements of each chevron are unfused except in case of the second 
and third which are united at their origin medially. Their antero-posterior 
extent is much greater in Gymnura. In Solenodon the two lateral elements of 
the first chevron are thin terete spicules of bone, approximated distally but 
separate. The second chevron is similar but the two elements are fused both 
proximally and distally forming a closed canal for the caudal artery. The same 
condition prevails in the two following, whose distal parts are in addition ex- 
panded laterally. In all the sueceeding chevron bones the arterial canal is 
open ventrally. The last chevron is between the 21st and the 22d caudals. 
In Solenodon cubanus Peters has figured but twenty chevron bones. There are 
21 in S. paradoxus. 
The ribs and sternum (Plate 7, figs. 11, 12) of Solenodon are remarkably 
strong and well ossified. The sternal portions of the first twelve ribs are bony, 
while the thirteenth is cartilaginous at the distal end only. The two succeeding 
ribs are connected by a cartilaginous strand to the ventral margin of the other 
sternal ribs, while the 16th rib is short and without such connection. The 
sternal portion of the first rib is broad at its articulation with the manubrium 
along the posterior curve of its antero-lateral expansion. The sternal portions 
of the three ribs following articulate each at the point of union of the first and 
second, second and third, and third and fourth sternal elements respectively 
The fifth rib is inserted at the Junction of the fourth and fifth sternal elements, 
and its sternal portion is of two separately ossified pieces. The fifth sternal 
element serves for the attachment, directly or secondarily of ribs 6 to 14 both 
inclusive. The sixth and seventh ribs are inserted separately, one directly in 
front of the other; the latter has three bony portions ventral to the main dorsal 
shaft. The sternal portions of ribs 8, 9, 10, and 11, have each a proximal section 
about 13 mm. long, making nearly a right angle with the more distal portion 
running antero-internally to the sternum and forming the ventral rim of the 
thoracic basket. These more distal pieces of these ribs just mentioned, are fused 
into a single bony mass, on whose ectal surface may be traced the lines of union, 
